In constructing a concrete road, after the road bed has been established, a first strip of concrete is poured which defines one lane of traffic for the road and typically has a width of about 12 feet. After the first strip of concrete is poured, a second strip is poured parallel to the first, and the second strip of concrete defines a second line of traffic. The process is repeated until the entire width of the road is completed. Each of the successive strips of concrete paving is joined to the preceding strip of pavement by a plurality of metal dowels, one end of which is inserted into bores drilled into the side of the slab of existing pavement and retained therein by epoxy or grout, and the other end of which is surrounded by the fresh concrete of the new pavement. Curbs, gutters and shoulders are also joined to the pavement with dowels.
The specification for concrete roadways generally require that the dowels be spaced twenty four or thirty inches apart. When a concrete roadway is patched by removing a portion of the slab and a replacement patch is poured, the specification generally require that dowels be spaced twelve inches apart along the edges of the patch.
To receive the dowels for attaching a new layer of pavement to an existing layer, holes must be drilled into the sides of the slab of the existing layer for receiving one end of the doweling rods. Two types of drilling machines are available which are capable of drilling such holes, one of which is hydraulically operated, and the other of which is pneumatically operated. Both drilling machines operate by rotating a drill bit into concrete while simultaneously axially hammering the drill bit into the hole. Both types of drilling machines also inject compressed air through a hollow drill to blow cuttings out of the hole being drilled. Currently, hydraulically operated machines are preferred over pneumatically operated machined because the pneumatically operated machines hammer with such a strong impact that damage is caused to the concrete. To operate effectively, the machines must be securely retained over the hole, and the machine must be axially moved toward the surface of the concrete as the hole is bored.
Several devices are available for retaining a plurality of parallel, spaced drilling machines oriented to drill into the side of a concrete slab. One of the most commonly used device has a skid for retaining four or five drilling machines and is manufactured by Woodings Doweling Technologies, Inc. of Mars, Pa. The controls for this device are mounted on the skid, and the skid is adapted to attach to the working end of a backhoe, which is in turn mounted on a tractor.
To operate the device, the tractor to which the backhoe is attached is positioned such that its direction of movement is perpendicular to the side of the pavement into which doweling holes are to be bored. The arm of the backhoe is then maneuvered to position the skid against the side of the concrete pavement with the drilling machines oriented to drill into the pavement side. Compressed air to blow cuttings out of the holes being drilled is received from an air compressor mounted on a second vehicle. One hole is drilled for each of the drilling machines, after which the backhoe must be rotated, and the skid repositioned to drill a second set of holes adjacent to the first set. Eventually, the backhoe with the device attached will drill properly spaced holes along the portion of the pavement which is reachable by the arm of the backhoe, a distance of perhaps 30 feet or more. Thereafter, the tractor and backhoe and associated air compressor must be repositioned near another length of roadway, and the process is repeated.
To operate such equipment, an operator is required to maneuver the vehicle and backhoe arm and a laborer is required to position the drilling machines and operate the controls for the drilling operation. The drilling process can be carried out by positioning the tractor and backhoe assembly off the concrete slab and on the adjacent grade with the drill machines extending away from the tractor or, alternately, by positioning the tractor on the slab with the backhoe arm extending beyond the edge of the slab and the drilling device oriented to drill towards the tractor. Generally, the tractor carrying the device is more easily maneuvered on the concrete slab than it is on the adjacent grade and, therefore, whenever possible, drilling is carried out with the tractor positioned on the slab. It is also desirable to drill the holes into relatively fresh concrete, that is, concrete which has not been fully cured, a process which requires several days.
Fresh concrete is softer than fully cured concrete and, therefore, the drilling process will be less time consuming, and the drill bits used in the process will have a longer useful life. On the other hand, fresh concrete cannot bear the same load that cured concrete can bear, and the specifications for building roads typically prohibit the use of vehicles in excess of 8,000 pounds on fresh concrete poured within the preceding 24 hours. A doweling hole drilling machine which is mounted on a backhoe typically has a weight in excess of 8,000 and usually cannot be used on fresh concrete.
Another type of machine used for drilling doweling holes has a frame with a plurality of drilling machines mounted thereon, and the frame is positioned between pairs of wheels such that it is movable like a vehicle. Such machines are manufactured by Minnich Maginnis Company of Mansfield, Ohio. These machines are relatively light weight and can be used on fresh concrete. The operation of existing wheel mounted doweling hole drilling machines requires that the vehicle be carefully positioned relative to the edge of the concrete in order that the ends of all the drilling machines abut against the side of a slab before the drilling commences. To drill a second set of holes adjacent to a first set of holes, the machine is repositioned by first moving it away from the concrete slab so that the machine will not scrape against the side of the concrete as it is moved to the next drilling location. Existing wheel mounted doweling hole drilling machines are pneumatically operated and a second vehicle having an air compressor thereon must accompany the machine to provide compressed air. These devices again require two operators. It would be desirable to provide a dowel hole drilling machine which could be operated by a single operator and which would overcome the problems of existing dowel hole drilling machines.